Coil and blower cleaning
If you want a duct-adjacent job with a measurable payback, this is it. The efficiency loss people blame on dirty ducts is usually sitting on the evaporator coil.
Where the loss is
Why the coil matters and the duct walls don't
An air conditioner works by moving heat across the surface of the evaporator coil. That coil is a dense array of fins with very little space between them, sitting directly in the airstream, permanently wet with condensate while the system runs.
Wet surface plus moving air full of fine dust equals a coating that builds up and hardens. Two things happen. Airflow through the fins drops, so the system moves less air. And the insulating layer means less heat crosses into the refrigerant, so each unit of electricity buys less cooling.
Compare that with a duct wall. Dust on the inside of a duct is not in the heat exchange path and is not restricting a narrow gap. It affects almost nothing thermally. That asymmetry is why we rank this above duct cleaning.
The blower wheel
The blower wheel
The other component nobody looks at. A blower wheel is a squirrel-cage fan with dozens of small curved blades, and each blade accumulates a layer of felted dust over years.
The buildup changes the blade profile, so the wheel moves less air per revolution. Airflow falls across the entire system. People respond by turning the thermostat down, which makes the unit run longer, which pulls more dust through. A heavily loaded wheel can also go out of balance, which you hear as vibration and which shortens the motor's life.
It is unpleasant to clean properly, since the wheel usually has to come out, which is why it gets skipped.
The warning signs
Signs it needs doing
- The system runs much longer than it used to for the same thermostat setting.
- Weak airflow from every register, not just one. One weak room is a duct problem; all of them is an air handler problem.
- The system freezes up: ice on the coil or the line. Restricted airflow is a leading cause.
- A musty smell when the system starts, from biological growth on a permanently damp fouled coil.
- Water where it should not be, because a clogged drain pan overflows.
- Electricity bills rising year on year with no change in habits or rate plan.
The work
What proper cleaning involves
The coil is accessed, which sometimes means cutting an access panel the original installer did not provide, and cleaned with a coil-specific cleaner appropriate to the fouling, then rinsed. Fins that have been bent flat by a previous careless cleaning get combed straight, since bent fins restrict airflow exactly like dirt does.
The drain pan and condensate line are cleared, which matters in Arlington's humidity: a system pulling gallons of water out of the air daily will back up if that line is partially blocked.
The blower wheel is pulled and cleaned off the machine. Wiping the accessible face while it sits in place is not the job. The buildup is on the inside curve of each blade.
Straight answers
Coil and blower questions
Isn't this what an annual service covers?
A basic tune-up usually checks refrigerant pressures, electrical connections and the condensate line. Proper coil and blower cleaning is a bigger job and is often a separate line item. Ask specifically what the tune-up includes.
How often?
Condition-based, not calendar-based. Have the coil looked at during any service visit and clean when it’s visibly fouled. In a dusty house with pets and a long cooling season, that comes round faster.
Can I clean the coil myself?
Not advisable. The fins bend if you look at them wrong, the wrong cleaner damages the aluminum, and access often requires opening a sealed cabinet. This is the one job here we would not suggest attempting.
Will it fix my musty smell?
Frequently, yes. The classic "dirty sock" smell usually comes from growth on a wet fouled coil, not from the ducts. That makes this the right first move rather than a whole-house duct clean.
What about a UV light?
A coil-facing UV lamp can slow regrowth on a clean coil. It’s not a substitute for cleaning a fouled one, and installing it over existing buildup accomplishes very little.
Start with a survey, not a sales visit
Ask about the coil and blower
A musty smell, ice on the line, or a system that runs constantly all point here rather than at the ducts. Describe what it is doing and when it started.
Related work we arrange
Other work worth considering
Air duct cleaning
Whole-system source removal to the NADCA method: negative pressure on the trunk, agitation in every branch. Not a vacuum poked into a vent.
Dryer vent cleaning
The one job in this trade with a documented fire-safety case behind it. Long duct runs in Arlington two-story homes make it worse.
Duct mold inspection
One of the three conditions the EPA says does warrant cleaning. Testing first, because "it looks like mold" is not a diagnosis.
Duct sealing and repair
Leaky ducts in a hot Arlington attic dump conditioned air where nobody lives. Usually a bigger saving than cleaning, and rarely offered.